Extended Endoscopic Endonasal Clipping of Basilar Apex Aneurysms: Anatomical Comparative Study and Surgical Simulation

Background Aneurysms of the posterior cerebral circulation constitutes 10% of intracranial aneurysms. Basilar apex (BA) aneurysms poses significant challenge in their management, not only because of their deep location and close proximity to the brain stem, cranial nerves, and thalamic perforators but also due to the complex intrinsic anatomical diversity of the basilar artery and its bifurcation. Different skull base approaches have been described for clipping of BA aneurysms, with the most common approaches being the orbitozygomatic approach and the subtemporal approach. Each approach has its advantages and shortcomings. With the recent dramatic advancement in the field of endoscopic endonasal skull base surgery, it has been widely implemented for surgical management of different skull base pathologies; nonetheless, their application for management of intracranial aneurysms is still debatable.

Objective The aim of this anatomical study is to compare between the transcranial orbitozygomatic and subtemporal approaches, and the endoscopic endonasal approach (EEA) for surgical clipping of BA aneurysms.

Methods Ten latex-injected cadaveric heads were used for dissection in an anatomical laboratory. An aneurysm simulation model with two different sizes was used at the BA in all specimens. Microsurgical dissection for orbitozygomatic and subtemporal approaches was performed on the same side in all specimens; followed by transclival/transdorsum sellae EEA with and without pituitary gland transposition, with the use of 0- and 45-degree rigid rod lens endoscopes (Karl Storz, Tuttlingen, Germany) connected to a high definition camera and 21-inch screen. Neuronavigation system and high-speed drills were utilized in all specimens. The key measured parameters for the comparative analysis of the three approaches were “depth of the surgical corridor,” “angle of attack,” “surgical freedom of instruments manipulation,” “the ability to obtain safe proximal control,” and “the ability of safe clip placement” according to the size and direction of the aneurysm simulation model, and the anatomical position of the BA in relation to the dorsum sellae.

Results EEA through a focal transclival/transdorsum sellae approach with pituitary gland transposition provides excellent wide exposure of the distal segment of the basilar artery and its bifurcation, with good amount of freedom of surgical instruments. Aneurysm models of the BA could be safely clipped via EEA after obtaining proximal control with improved visualization of perforating branches.

Conclusion EEA provides a direct wide access to the BA, regardless of its anatomical position. EEA can be considered a feasible option for the surgical clipping of superiorly and ventrally directed BA aneurysms in select patients.